U.S. patent application number 12/034288 was filed with the patent office on 2008-08-21 for ceramic-coated member and production method thereof.
Invention is credited to Toshiaki Fuse, Yutaka Ishiwata, Kunihiko Wada.
Application Number | 20080199709 12/034288 |
Document ID | / |
Family ID | 39488291 |
Filed Date | 2008-08-21 |
United States Patent
Application |
20080199709 |
Kind Code |
A1 |
Ishiwata; Yutaka ; et
al. |
August 21, 2008 |
CERAMIC-COATED MEMBER AND PRODUCTION METHOD THEREOF
Abstract
A ceramic-coated member is configured by laminating at least a
thermal stress relieving layer 22 and a thermal barrier layer 23 in
this order on a base material 20 of metal or ceramic. A density of
zirconium oxide forming the thermal stress relieving layer 22
decreases continuously and a density of hafnium oxide forming the
thermal barrier layer 23 increases continuously from the thermal
stress relieving layer 22 toward the thermal barrier layer 23 in a
boundary portion 24 and its neighborhood between the thermal stress
relieving layer 22 and the thermal barrier layer 23.
Inventors: |
Ishiwata; Yutaka;
(Zushi-shi, JP) ; Fuse; Toshiaki; (Tokyo, JP)
; Wada; Kunihiko; (Yokohama-shi, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER;LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
39488291 |
Appl. No.: |
12/034288 |
Filed: |
February 20, 2008 |
Current U.S.
Class: |
428/457 ;
427/596; 428/411.1; 428/702 |
Current CPC
Class: |
Y10T 428/31678 20150401;
C23C 28/36 20130101; C23C 14/30 20130101; C23C 14/246 20130101;
C23C 28/321 20130101; C23C 28/3455 20130101; C23C 14/083 20130101;
C23C 28/345 20130101; Y02T 50/60 20130101; Y10T 428/31504 20150401;
C23C 14/025 20130101 |
Class at
Publication: |
428/457 ;
428/411.1; 428/702; 427/596 |
International
Class: |
B32B 15/04 20060101
B32B015/04; B32B 9/04 20060101 B32B009/04; C23C 14/30 20060101
C23C014/30 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2007 |
JP |
P2007-039277 |
Claims
1. A ceramic-coated member which is configured by laminating at
least a thermal stress relieving layer and a thermal barrier layer
in this order on a base material made of metal or ceramic, wherein
a density of a first ceramic material which forms the thermal
stress relieving layer decreases continuously and a density of a
second ceramic material which forms the thermal barrier layer
increases continuously from the thermal stress relieving layer
toward the thermal barrier layer in a boundary layer between the
thermal stress relieving layer and the thermal barrier layer.
2. The ceramic-coated member according to claim 1, wherein an
oxidation resistant layer made of metal is interposed between the
base material and the thermal stress relieving layer.
3. The ceramic-coated member according to claim 1, wherein the
first ceramic material has a thermal expansion coefficient which is
larger than that of the second ceramic material.
4. The ceramic-coated member according to claim 1, wherein the
first ceramic material has zirconium oxide as a main component, and
the second ceramic material has hafnium oxide as a main
component.
5. The ceramic-coated member according to claim 1, wherein layers
which are formed of the individual ceramic materials are formed by
electron-beam physical vapor deposition.
6. A ceramic-coated member which is configured by laminating at
least an oxygen barrier layer, a thermal stress relieving layer and
a thermal barrier layer in this order on a base material made of
metal or ceramic, wherein a density of a third ceramic material
which forms the oxygen barrier layer decreases continuously and a
density of a first ceramic material which forms the thermal stress
relieving layer increases continuously from the oxygen barrier
layer toward the thermal stress relieving layer in a boundary layer
between the oxygen barrier layer and the thermal stress relieving
layer; and wherein the density of the first ceramic material which
forms the thermal stress relieving layer decreases continuously and
a density of a second ceramic material which forms the thermal
barrier layer increases continuously from the thermal stress
relieving layer toward the thermal barrier layer in a boundary
layer between the thermal stress relieving layer and the thermal
barrier layer.
7. The ceramic-coated member according to claim 6, wherein an
oxidation resistant layer made of metal is interposed between the
base material and the oxygen barrier layer.
8. The ceramic-coated member according to claim 6, wherein the
first ceramic material has a thermal expansion coefficient which is
larger than that of the second ceramic material.
9. The ceramic-coated member according to claim 6, wherein the
first ceramic material has zirconium oxide as a main component, and
the second ceramic material has hafnium oxide as a main
component.
10. The ceramic-coated member according to claim 6, wherein the
third ceramic material has aluminum oxide as a main component.
11. The ceramic-coated member according to claim 6, wherein layers
which are formed of the individual ceramic materials are formed by
electron-beam physical vapor deposition.
12. A production method of a ceramic-coated member by laminating at
least a thermal stress relieving layer of a first ceramic material
and a thermal barrier layer of a second ceramic material in this
order on a base material of metal or ceramic by electron-beam
physical vapor deposition, wherein an ingot, which has the first
ceramic material and the second ceramic material disposed by
columnarly stacking and an interface between the first ceramic
material and the second ceramic material configured with a
prescribed angle with respect to the central axis of the columnar
stacked body so to have the first ceramic material on the side to
evaporate first, is used to form the thermal stress relieving layer
and the thermal barrier layer.
13. A production method of a ceramic-coated member by laminating at
least an oxygen barrier layer of a third ceramic material, a
thermal stress relieving layer of a first ceramic material and a
thermal barrier layer of a second ceramic material in this order on
a base material of metal or ceramic by electron-beam physical vapor
deposition, wherein an ingot, which has the third ceramic material,
the first ceramic material and the second ceramic material disposed
by columnarly stacking in this order and an interface between the
third ceramic material and the first ceramic material and an
interface between the first ceramic material and the second ceramic
material configured with a prescribed angle with respect to the
central axis of the columnar stacked body so to have the third
ceramic material on the side to evaporate first, is used to form
the oxygen barrier layer, the thermal stress relieving layer and
the thermal barrier layer.
14. The production method of a ceramic-coated member according to
claim 12, wherein an oxidation resistant layer of metal is
previously formed on a surface of the base material.
15. The production method of a ceramic-coated member according to
claim 13, wherein an oxidation resistant layer of metal is
previously formed on a surface of the base material.
16. The production method of a ceramic-coated member according to
claim 12, wherein the prescribed angle is in a range of 45.degree.
to 85.degree..
17. The production method of a ceramic-coated member according to
claim 13, wherein the prescribed angle is in a range of 45.degree.
to 85.degree..
18. The production method of a ceramic-coated member according to
claim 12, wherein the first ceramic material has a thermal
expansion coefficient which is larger than that of the second
ceramic material.
19. The production method of a ceramic-coated member according to
claim 13, wherein the first ceramic material has a thermal
expansion coefficient which is larger than that of the second
ceramic material.
20. The production method of a ceramic-coated member according to
claim 12, wherein the first ceramic material has zirconium oxide as
a main component, and the second ceramic material has hafnium oxide
as a main component.
21. The production method of a ceramic-coated member according to
claim 13, wherein the first ceramic material has zirconium oxide as
a main component, and the second ceramic material has hafnium oxide
as a main component.
22. The production method of a ceramic-coated member according to
claim 12, wherein the third ceramic material has aluminum oxide as
a main component.
23. The production method of a ceramic-coated member according to
claim 13, wherein the third ceramic material has aluminum oxide as
a main component.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No. 2007-039277
filed on Feb. 20, 2007; the entire contents of which are
incorporated herein by reference.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to a coated member which is
coated with metal or ceramic material by electron-beam physical
vapor deposition and a manufacturing method thereof, and more
particularly to a ceramic-coated member, which has a member for
industrial gas turbines, jet engines and the like and exposed to
high temperatures improved in heat resistance, oxidation
resistance, heat cycle resistance and the like, and a manufacturing
method thereof.
[0004] 2. Description of the Related Art
[0005] High-temperature members such as rotor blades (blades),
stator vanes (vanes), combustors and the like for industrial gas
turbines, jet engines and the like are exposed to a combustion gas
of exceeding 1000.degree. C. Generally, such high-temperature
members are made of a heat-resistant alloy called a nickel-base
superalloy but their strength is deteriorated suddenly exceeds
1000.degree. C. Therefore, these high-temperature members are
controlled to a temperature of 950.degree. C. or below by cooling
their front and rear surfaces with a cooling medium such as air,
steam or the like. But, since a combustion efficiency and power
generation efficiency can be improved by increasing the combustion
gas temperature, the combustion gas temperatures of the industrial
gas turbines, jet engines and the like of these years are kept
increasing to 1300.degree. C. and further to 1500.degree. C.
Therefore, a conventional cooling method is hard to control the
high-temperature members to a temperature of 950.degree. C. or
below.
[0006] FIG. 8 shows a part of a sectional structure of a rotor
blade 200 which is used for the latest industrial gas turbines and
jet engines. FIG. 9 is a schematic view showing the effects of a
thermal barrier coating.
[0007] As shown in FIG. 8, the rotor blade 200 has a metal layer
220 having excellent corrosion and oxidation resistance coated on a
surface of a refractory metal member 210 and a ceramic layer 230
having a low thermal conductivity and an excellent thermal barrier
characteristic coated on a surface of the metal layer 220. The
metal layer 220 and the ceramic layer 230 function as a thermal
barrier coating layer 240. A surface of the ceramic layer 230 is in
contact with combustion gas, and a surface of the refractory metal
member 210, which is on the other side of the thermal barrier
coating layer 240, is in contact with a cooling medium.
[0008] As shown in FIG. 9, the rotor blade 200 is provided with a
large temperature gradient by the ceramic layer 230 to retard a
metal base material from having an increased temperature with an
increase in temperature of the combustion gas to a high level. In
FIG. 9, the horizontal axis indicates a distance from the surface
of the rotor blade 200 shown in FIG. 8, which is in contact with
the combustion gas, to the refractory metal member 210. The
vertical axis indicates a temperature of the rotor blade 200. The
ceramic material used for the ceramic layer 230 is desired to have
a low thermal conductivity and excellent heat resistance, and
zirconium oxide (ZrO.sub.2) which is stabilized with yttrium oxide
(Y.sub.2O.sub.3) is generally used extensively. This yttrium
oxide-stabilized zirconium oxide has a thermal conductivity of
about 2 W/(mK), which is about 1/10 to 1/100 of the thermal
conductivity of the metallic material. The yttrium oxide-stabilized
zirconium oxide has a thermal conductivity which is low among the
ceramic materials and can be lowered to about 1.4 W/(mK) by forming
a large number of pores in the coating film by plasma spraying at
the time of thermal barrier coating.
[0009] But, the surface of the thermal barrier coating layer 240 is
required to have excellent abrasion resistance and erosion
resistance because it is hit by solid particles such as oxide scale
at a high speed. Meanwhile, the surface of the metal layer 220 is
required to have excellent oxidation resistance because an oxide
layer grows and causes delamination of the ceramic layer 230.
Besides, since the rotor blade 200 is exposed to a high temperature
for a long time, a thermal stress is generated repeatedly because
of a thermal expansion difference between the metal layer 220 and
the ceramic layer 230 with the start and stop. And, the
delamination of the ceramic layer 230 is accelerated. Therefore, it
is required to relieve the thermal stress.
[0010] As described above, the thermal barrier coating which is
applied to the high-temperature member such as the rotor blade 200
is demanded to have various characteristics, and the above demands
are hardly satisfied by a simple combination of the metal layer and
the ceramic layer. Accordingly, the thermal barrier coating layer
is multilayered to share the functions of the individual layers,
thereby satisfying the above demands.
[0011] For example, JP-A 2003-41358 discloses a metallic part
having a multilayer structure of a barrier layer, a hot gas
corrosion protection layer, a protection layer, a heat barrier
layer and a flat and smooth layer. JP-A 2001-348655 discloses a gas
turbine member which has a double-layered structure of a ceramic
layer having a high strength and high toughness and a ceramic layer
having high temperature stability. And, JP-A 2006-124226 discloses
a ceramic part for a gas turbine, which has a close adhesion
promoting layer, a stress relieving layer, a crack development
preventive layer and a surface corrosion-resistant layer.
[0012] The coating on the above-described conventional
high-temperature parts is formed by thermal spraying. For example,
JP-A 2005-313644 also discloses metallic parts which have a thermal
barrier coating formed by the electron-beam physical vapor
deposition. This electron-beam physical vapor deposition forms the
coating by growing the evaporated coating material on the substrate
to obtain columnar ceramic structure and is excellent in a thermal
stress relieving property in comparison with the case that the
thermal spraying is performed.
[0013] FIG. 10 shows a diagram for illustrating an overview of the
electron-beam physical vapor deposition. FIG. 11A schematically
shows a change in characteristic X-ray intensity (corresponding to
the density of ceramic material A) in the thickness direction in
the vicinity of an interface between a ceramic material A layer and
a ceramic material B layer when the gradient composition layer of
two types of ceramic materials (A, B) is formed by using a thermal
spraying method. And, FIG. 11B is a diagram schematically showing a
change in characteristic X-ray intensity (corresponding to the
density of the ceramic material A) in the thickness direction in
the vicinity of the interface between the ceramic material A layer
and the ceramic material B layer when the gradient composition
layer of two types of ceramic materials (A, B) is formed by the
electron-beam physical vapor deposition.
[0014] For the electron-beam physical vapor deposition shown in
FIG. 10, two kind of ingots, namely evaporation targets 250a and
250b, are prepared, and the output of an electron beam 260 is
gradually varied to control the evaporated quantity of vapor 270,
thereby forming the gradient composition layer. In the gradient
composition layer formed by the electron-beam physical vapor
deposition, the characteristic X-ray intensity in the thickness
direction in the vicinity of the interface between the ceramic
material A layer and the ceramic material B layer has a
considerably uneven intensity distribution as shown in FIG. 11B.
Meanwhile, in the gradient composition layer formed by the thermal
spraying method, the characteristic X-ray intensity in the
thickness direction in the vicinity of the interface between the
ceramic material A layer and the ceramic material B layer has a
step-like intensity distribution as shown in FIG. 11A.
[0015] It is significant for the above-described multi-layer
coating to relieve a thermal stress due to adhesiveness between the
individual coatings, consistency of a crystal structure and a
thermal expansion difference and, for that, to have ideally a
gradient composition structure that the composition of the
interface between the individual coatings is continuously
variable.
[0016] The thermal spraying which is a conventional thermal barrier
coating method changes stepwise the compounding ratio of thermal
spraying powder to provide a gradient composition and requires
exchanging the thermal spraying powder every time the composition
is changed. Therefore, as described above, the characteristic X-ray
intensity in the thickness direction in the vicinity of the
interface between the ceramic material A layer and the ceramic
material B layer of the gradient composition layer becomes a
step-like intensity distribution, and the composition cannot be
changed continuously.
[0017] According to the conventional electron-beam physical vapor
deposition, the vapor amount of an evaporation target with respect
to the electron beam power and evaporating rate are not necessarily
constant, and a time lag is also caused in evaporation of both the
evaporation targets. Therefore, the characteristic X-ray intensity
in the thickness direction in the vicinity of the interface between
the ceramic material A layer and the ceramic material B layer of
the gradient composition layer becomes to have a considerably
uneven intensity distribution, and the composition cannot be
changed continuously as described above.
BRIEF SUMMARY OF THE INVENTION
[0018] The present invention provides a ceramic-coated member
excelling in thermal barrier characteristic and heat cycle life and
having a gradient composition structure with a continuously
variable composition of an interface between individual coatings
formed by electron beam physical vapor deposition, and a production
method thereof.
[0019] According to an aspect of the present invention, there is
provided a ceramic-coated member which is configured by laminating
at least a thermal stress relieving layer and a thermal barrier
layer in this order on a base material made of metal or ceramic,
wherein a density of a first ceramic material which forms the
thermal stress relieving layer decreases continuously and a density
of a second ceramic material which forms the thermal barrier layer
increases continuously from the thermal stress relieving layer
toward the thermal barrier layer in a boundary layer between the
thermal stress relieving layer and the thermal barrier layer.
[0020] According to another aspect of the present invention, there
is provided a ceramic-coated member which is configured by
laminating at least an oxygen barrier layer, a thermal stress
relieving layer and a thermal barrier layer in this order on a base
material made of metal or ceramic, wherein a density of a third
ceramic material which forms the oxygen barrier layer decreases
continuously and a density of a first ceramic material which forms
the thermal stress relieving layer increases continuously from the
oxygen barrier layer toward the thermal stress relieving layer in a
boundary layer between the oxygen barrier layer and the thermal
stress relieving layer; and the density of the first ceramic
material which forms the thermal stress relieving layer decreases
continuously and a density of a second ceramic material which forms
the thermal barrier layer increases continuously from the thermal
stress relieving layer toward the thermal barrier layer in a
boundary layer between the thermal stress relieving layer and the
thermal barrier layer.
[0021] According to another aspect of the present invention, there
is provided a production method of a ceramic-coated member by
laminating at least a thermal stress relieving layer of a first
ceramic material and a thermal barrier layer of a second ceramic
material in this order on a base material of metal or ceramic by
electron-beam physical vapor deposition, wherein an ingot, which
has the first ceramic material and the second ceramic material
disposed by columnarly stacking and an interface between the first
ceramic material and the second ceramic material configured with a
prescribed angle with respect to the central axis of the columnar
stacked body so to have the first ceramic material on the side to
evaporate first, is used to form the thermal stress relieving layer
and the thermal barrier layer.
[0022] According to another aspect of the present invention, there
is provided a production method of a ceramic-coated member by
laminating at least an oxygen barrier layer of a third ceramic
material, a thermal stress relieving layer of a first ceramic
material and a thermal barrier layer of a second ceramic material
in this order on a base material of metal or ceramic by
electron-beam physical vapor deposition, wherein an ingot, which
has the third ceramic material, the first ceramic material and the
second ceramic material disposed by columnarly stacking in this
order and an interface between the third ceramic material and the
first ceramic material and an interface between the first ceramic
material and the second ceramic material configured with a
prescribed angle with respect to the central axis of the columnar
stacked body so to have the third ceramic material on the side to
evaporate first, is used to form the oxygen barrier layer, the
thermal stress relieving layer and the thermal barrier layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] The present invention is described with reference to the
drawings, which are provided for illustration only and do not limit
the present invention in any respect.
[0024] FIG. 1 is a diagram showing a cross section of a
ceramic-coated member of a first embodiment.
[0025] FIG. 2 is a sectional view showing an overview of
electron-beam physical vapor deposition for producing the
ceramic-coated member.
[0026] FIG. 3 is a diagram showing a cross section of a
ceramic-coated member of a second embodiment.
[0027] FIG. 4 is a sectional view showing an overview of
electron-beam physical vapor deposition for producing the
ceramic-coated member.
[0028] FIG. 5 is a diagram showing a reflected electron image
obtained by observing a cross section of a test piece 3 through an
SEM in Example 3.
[0029] FIG. 6 is a diagram showing the results of measurement of
element distribution in a boundary portion and its neighborhood of
the test piece 3 conducted in Example 3.
[0030] FIG. 7 is a diagram showing a relationship between an angle
.theta. formed by an interface between a zirconium oxide ingot and
a hafnium oxide ingot with respect to the central axis of a
columnar stacked body and a thickness of a gradient composition
layer formed when an ingot having that angle is used.
[0031] FIG. 8 shows a part of a sectional structure of a rotor
blade which is used for the latest industrial gas turbines and jet
engines.
[0032] FIG. 9 is a schematic view showing the effects of a thermal
barrier coating.
[0033] FIG. 10 is a diagram for illustrating an overview of the
electron-beam physical vapor deposition.
[0034] FIG. 11A is a diagram schematically showing a change in
characteristic X-ray intensity in the thickness direction in the
vicinity of an interface between a ceramic material A layer and a
ceramic material B layer when a gradient composition layer of two
types of ceramic materials (A, B) is formed by using a thermal
spraying method.
[0035] FIG. 11B is a diagram schematically showing a change in
characteristic X-ray intensity in the thickness direction in the
vicinity of the interface between the ceramic material A layer and
the ceramic material B layer when a gradient composition layer of
two types of ceramic materials (A, B) is formed by electron-beam
physical vapor deposition.
DETAILED DESCRIPTION OF THE INVENTION
[0036] Embodiments of the present invention will be described below
with reference to the figures.
First Embodiment
[0037] FIG. 1 is a diagram showing a cross section of a
ceramic-coated member 10 of the first embodiment.
[0038] As shown in FIG. 1, the ceramic-coated member 10 has a base
material 20, an oxidation resistant layer 21 stacked on the base
material 20, a thermal stress relieving layer 22 stacked on the
oxidation resistant layer 21, and a thermal barrier layer 23
stacked on the thermal stress relieving layer 22.
[0039] A boundary portion 24 and its neighborhood between the
thermal stress relieving layer 22 and the thermal barrier layer 23
are configured such that a density of a ceramic material which
forms the thermal stress relieving layer 22 decreases continuously
from the thermal stress relieving layer 22 toward the thermal
barrier layer 23 and a density of a ceramic material which forms
the thermal barrier layer 23 increases continuously. The boundary
portion 24 and its neighborhood function as a boundary layer.
[0040] For example, the base material 20 is comprised of a
heat-resistant metallic material such as an Ni-base superalloy and
a ceramic material such as silicon nitride. The base material 20
includes, for example, members to be exposed to a high-temperature
combustion gas of industrial gas turbines, jet engines and the like
but is not limited to them and may be a high-temperature member
requiring a ceramic coating.
[0041] The oxidation resistant layer 21 is a coating which
suppresses an oxide from generating on the surface of the base
material 20 and improves its bonding property to the thermal stress
relieving layer 22 and is comprised of a metallic material
excelling in corrosion resistance, oxidation resistance and crack
propagation resistance. The oxidation resistant layer 21 is formed
of, for example, a Ni-base alloy, a Co-base alloy and an
Ni--Co-base alloy to which Cr, Al and Y are added at a prescribed
ratio. The oxidation resistant layer 21 is formed on the surface of
the base material 20 by plasma spraying or the like.
[0042] The thermal stress relieving layer 22 is a coating formed of
a ceramic material having a thermal expansion coefficient larger
than that of the thermal barrier layer 23. As a ceramic material
which forms the coating, for example, a stabilized zirconium
oxide-based ceramic material having zirconium oxide (ZrO.sub.2) as
a main component is used. To the zirconium oxide is added as a
stabilizing agent, for example, an oxide of a rare-earth element
such as yttria (Y.sub.2O.sub.3), ceria (Ce.sub.2O.sub.3) or the
like.
[0043] The thermal barrier layer 23 is a coating formed of a
ceramic material having excellent heat resistance and low thermal
conductivity. As a ceramic material forming the coating, for
example, a stabilized hafnium oxide-based ceramic material having
hafnium oxide (HfO.sub.2) as a main component is used. To the
hafnium oxide is also added as a stabilizing agent, for example, an
oxide of a rare-earth element such as yttria (Y.sub.2O.sub.3),
ceria (Ce.sub.2O.sub.3) or the like.
[0044] In the boundary portion 24 and its neighborhood between the
thermal stress relieving layer 22 and the thermal barrier layer 23,
the density of the zirconium oxide forming the thermal stress
relieving layer 22 decreases continuously and the density of the
hafnium oxide forming the thermal barrier layer 23 increases
continuously from the thermal stress relieving layer 22 toward the
thermal barrier layer 23. In other words, the boundary portion 24
and its neighborhood between the thermal stress relieving layer 22
and the thermal barrier layer 23 form a gradient composition layer
which has the densities of zirconium oxide and hafnium oxide
changed continuously in the thickness direction. Considering the
generation of, for example, a thermal stress, the thickness of the
gradient composition layer is preferably about 1/4 of the thickness
of the ceramic layer which is formed of the thermal stress
relieving layer 22 and the thermal barrier layer 23. Meanwhile,
considering the thermal barrier characteristic, the thickness of
the gradient composition layer is preferably about 1/2 of the
thickness of the ceramic layer which is formed of the thermal
stress relieving layer 22 and the thermal barrier layer 23. The
thickness of the gradient composition layer is not limited to the
above but may be determined appropriately in response to the
demands for the base material 20.
[0045] A production method of the ceramic-coated member 10 will be
described below with reference to FIG. 2.
[0046] FIG. 2 is a sectional view showing an overview of
electron-beam physical vapor deposition (EB-PVD) for producing the
ceramic-coated member 10.
[0047] First, the oxidation resistant layer 21 formed of the
above-described metallic material is formed on a surface of the
base material 20 by plasma spraying or the like.
[0048] Subsequently, the thermal stress relieving layer 22 and the
thermal barrier layer 23 which are formed on the oxidation
resistant layer 21 are formed by the electron-beam physical vapor
deposition. A method of forming the thermal stress relieving layer
22 and the thermal barrier layer 23 is concretely described
below.
[0049] The electron-beam physical vapor deposition forms a ceramic
coating on a surface of the oxidation resistant layer 21 which is
heated to a high temperature by irradiating an electron beam 45 to
an ingot 40, which is formed of ceramic in vacuum, to melt the
ingot surface so to produce the vapor 46 of ingot material. At this
time, the base material 20 is rotated in a prescribed direction at
a constant speed with its central axis determined as the rotation
axis such that the surface of the oxidation resistant layer 21 can
be uniformly ceramic-coated as shown in FIG. 2. For example, in a
case where this method is used for ceramic coating, a coating
having a thickness of 200 to 300 .mu.m is generally formed at a
coating speed of about 100 .mu.m/h (a coating thickness formed in
one hour). Meanwhile, the rotation speed of the base material 20 is
set to about 10 rpm (rotations per minute). In other words, the
coating thickness per rotation becomes about 0.17 .mu.m, and in a
case where the base material 20 is rotated to perform coating, a
good gradient composition layer can be formed regardless of a
portion of the base material 20.
[0050] The ingot 40 is placed in a water-cooled crucible 50 with a
zirconium oxide ingot 41 and a hafnium oxide ingot 42 columnarly
stacked such that the zirconium oxide ingot 41 is evaporated first.
And, the ingot 40 is configured so that the interface between the
zirconium oxide ingot 41 and the hafnium oxide ingot 42 has a
prescribed angle .theta. with respect to the central axis of the
columnar stacked body.
[0051] Here, the prescribed angle .theta. is preferably 45.degree.
to 85.degree.. This angle .theta. is preferable because if it is
less than 45.degree., the gradient composition layer has a
thickness larger than the required thickness. In other words, the
coating as a whole has a greater thickness, the film forming time
period becomes long, and the coating tends to be delaminated. If
the coating thickness as a whole is previously determined, the
required thickness of the thermal barrier layer becomes thin.
Meanwhile, if that angle exceeds 85.degree., the effect of
providing the interface with the angle is impaired, and the
continuous gradient composition cannot be formed.
[0052] As described above, the interface between the zirconium
oxide ingot 41 and the hafnium oxide ingot 42 is configured to have
the prescribed angle .theta. with respect to the central axis of
the columnar stacked body, so that the vapor 46 of the composition
containing both components zirconium oxide and hafnium oxide can be
formed when that portion becomes the vapor 46. At the time when the
ingot 40 is evaporated at the portion having the prescribed angle
.theta., the component composition of the vapor 46 has the density
of the hafnium oxide increased continuously as the density of the
zirconium oxide decreases continuously. Thus, between the thermal
stress relieving layer 22 and the thermal barrier layer 23 is
formed the gradient composition layer in that the density of the
zirconium oxide forming the thermal stress relieving layer 22
decreases continuously and the density of the hafnium oxide forming
the thermal barrier layer 23 increases continuously from the
thermal stress relieving layer 22 toward the thermal barrier layer
23.
[0053] Adjustment of the above-described prescribed angle .theta.
allows adjustment of the thickness of the gradient composition
layer and the density gradient of the zirconium oxide and the
hafnium oxide in the gradient composition layer. Besides, the
stacked quantity of the zirconium oxide ingot 41 or the hafnium
oxide ingot 42 at a portion other than the portion contacted at the
prescribed angle .theta. in the ingot 40 can be adjusted to control
the thickness of the thermal stress relieving layer 22 or the
thermal barrier layer 23. Depending on the characteristics such as
heat cycle life, thermal barrier characteristic, thermal shock
resistance and the like which are required for the base material 20
to be coated, a coating can be applied by appropriately adjusting
the prescribed angle .theta. in the ingot 40 and the stacked
quantity of the zirconium oxide ingot 41 or the hafnium oxide ingot
42 at the portion other than the portion contacted at the
prescribed angle .theta..
[0054] As described above, the boundary portion 24 and its
neighborhood between the thermal stress relieving layer 22 and the
thermal barrier layer 23 of the ceramic-coated member 10 of the
first embodiment can be formed as the gradient composition layer
where the density of the zirconium oxide which forms the thermal
stress relieving layer 22 is decreased continuously and the density
of the hafnium oxide which forms the thermal barrier layer 23 is
increased continuously from the thermal stress relieving layer 22
toward the thermal barrier layer 23. Thus, the concentration of a
thermal stress in the contacted part of the coatings of the
different materials is relieved, and the heat cycle characteristic
can be improved substantially.
[0055] A surface of the ceramic-coated member 10 is formed of the
thermal barrier layer 23 which is formed of hafnium oxide having
excellent heat resistance and low thermal conductivity, and the
metal layer side is formed of the thermal stress relieving layer 22
which is formed of zirconium oxide having low thermal conductivity
and a thermal expansion coefficient larger than that of the hafnium
oxide and stacked on the thermal barrier layer 23. Thus, it becomes
possible to maintain the excellent thermal barrier characteristic
even if the ceramic-coated member 10 is used at a high temperature
for a long time.
[0056] The above-described ceramic-coated member 10 having the
gradient composition layer (the boundary portion 24 and its
neighborhood) can be produced by using the ingot 40 having the
zirconium oxide ingot 41 and the hafnium oxide ingot 42 stacked in
a columnar form such that the first evaporating side becomes the
zirconium oxide ingot 41 by the electron-beam physical vapor
deposition and the interface between the zirconium oxide ingot 41
and the hafnium oxide ingot 42 determined to have a prescribed
angle .theta. with respect to the central axis of the columnar
stacked body.
Second Embodiment
[0057] FIG. 3 is a diagram showing a cross section of a
ceramic-coated member 60 of the second embodiment. Like component
parts corresponding to those of the ceramic-coated member 10 of the
first embodiment are denoted by like reference numerals, and
overlapped descriptions will be omitted or simplified.
[0058] As shown in FIG. 3, the ceramic-coated member 60 has the
base material 20, the oxidation resistant layer 21 which is
laminated on the base material 20, an oxygen barrier layer 70 which
is laminated on the oxidation resistant layer 21, the thermal
stress relieving layer 22 which is laminated on the oxygen barrier
layer 70, and the thermal barrier layer 23 which is laminated on
the thermal stress relieving layer 22.
[0059] In a boundary portion 71 and its neighborhood between the
oxygen barrier layer 70 and the thermal stress relieving layer 22,
it is configured such that the density of a ceramic material which
forms the oxygen barrier layer 70 decreases continuously and the
density of a ceramic material which forms the thermal stress
relieving layer 22 increases continuously from the oxygen barrier
layer 70 toward the thermal stress relieving layer 22. Besides, in
the boundary portion 24 and its neighborhood between the thermal
stress relieving layer 22 and the thermal barrier layer 23, the
density of the ceramic material which forms the thermal stress
relieving layer 22 decreases continuously and the density of a
ceramic material which forms the thermal barrier layer 23 increases
continuously from the thermal stress relieving layer 22 toward the
thermal barrier layer 23. The boundary portion 71 and its
neighborhood function as a boundary layer.
[0060] The oxygen barrier layer 70 is a coating formed of a ceramic
material which is excellent in prevention of oxygen permeation from
the outside toward the oxidation resistant layer 21 and has a
thermal expansion coefficient larger than those of the ceramic
material having, as a main component, zirconium oxide which forms
the thermal stress relieving layer 22 and that of the ceramic
material having, as a main component, hafnium oxide which forms the
thermal barrier layer 23. As the ceramic material which forms the
coating, for example, an aluminum oxide-based ceramic material
which has aluminum oxide (Al.sub.2O.sub.3) as a main component is
used.
[0061] In the boundary portion 71 and its neighborhood between the
oxygen barrier layer 70 and the thermal stress relieving layer 22,
the density of the aluminum oxide which forms the oxygen barrier
layer 70 decreases continuously and the density of the zirconium
oxide which forms the thermal stress relieving layer 22 increases
continuously from the oxygen barrier layer 70 toward the thermal
stress relieving layer 22. In other words, the boundary portion 71
and its neighborhood between the oxygen barrier layer 70 and the
thermal stress relieving layer 22 form a gradient composition layer
where the densities of aluminum oxide and zirconium oxide change
continuously in the thickness direction. Besides, in the boundary
portion 24 and its neighborhood between the thermal stress
relieving layer 22 and the thermal barrier layer 23, the density of
the zirconium oxide which forms the thermal stress relieving layer
22 decreases continuously and the density of the hafnium oxide
which forms the thermal barrier layer 23 increases continuously
from the thermal stress relieving layer 22 toward the thermal
barrier layer 23. In other words, the boundary portion 24 and its
neighborhood between the thermal stress relieving layer 22 and the
thermal barrier layer 23 form a gradient composition layer where
the densities of zirconium oxide and hafnium oxide change
continuously in the thickness direction.
[0062] A production method of the ceramic-coated member 60 is
described with reference to FIG. 4.
[0063] FIG. 4 is a sectional view showing an overview of
electron-beam physical vapor deposition for production of the
ceramic-coated member 60.
[0064] First, the oxidation resistant layer 21 formed of the
above-described metallic material is formed on a surface of the
base material 20 by plasma spraying or the like.
[0065] Subsequently, the oxygen barrier layer 70, the thermal
stress relieving layer 22 and the thermal barrier layer 23 are
formed on the oxidation resistant layer 21 by the electron-beam
physical vapor deposition. A method of forming the oxygen barrier
layer 70, the thermal stress relieving layer 22 and the thermal
barrier layer 23 is specifically described below.
[0066] The electron-beam physical vapor deposition is performed by
irradiating an electron beam 45 to an ingot 65 which is formed of
ceramic in vacuum to melt the ingot surface so as to produce the
vapor 67 of ingot material, thereby forming a ceramic coating on a
surface of the oxidation resistant layer 21 which is heated to a
high temperature. At this time, the base material 20 is rotated in
a prescribed direction at a constant speed with the central axis of
the base material 20 determined as the rotation axis such that the
surface of the oxidation resistant layer 21 can be uniformly
ceramic-coated as shown in FIG. 4.
[0067] The ingot 65 is placed in a water-cooled crucible 50 by
columnarly stacking an aluminum oxide ingot 66, the zirconium oxide
ingot 41 and the hafnium oxide ingot 42 in this order such that the
aluminum oxide ingot 66 is evaporated first. And, an interface
between the aluminum oxide ingot 66 and the zirconium oxide ingot
41 and an interface between the zirconium oxide ingot 41 and the
hafnium oxide ingot 42 are configured to have prescribed angles
.theta. and .gamma. with respect to the central axis of the
columnar stacked body.
[0068] Here, the prescribed angles .theta. and .gamma. are
preferably 45.degree. to 85.degree.. The prescribed angles .theta.
are .gamma. are preferable because if they are less than
45.degree., the gradient composition layer has an increased
thickness and if they exceed 85.degree., the effect that the
interface is provided with the angle is impaired, and a continuous
gradient composition cannot be formed. Since this gradient
composition layer has high thermal conductivity, the gradient
composition layer is desired to be thin.
[0069] As described above, the interface between the aluminum oxide
ingot 66 and the zirconium oxide ingot 41 is configured to have the
prescribed angle .gamma. with respect to the central axis of the
columnar stacked body, so that the vapor 67 having a composition
containing both components, the aluminum oxide and the zirconium
oxide, can be formed at the time when the interface becomes the
vapor 67. The component composition of the vapor 67 at the time
when the ingot 65 at the portion having the prescribed angle
.gamma. is evaporated has the density of the aluminum oxide
decreased continuously as the density of the zirconium oxide
increases continuously. Thus, between the oxygen barrier layer 70
and the thermal stress relieving layer 22 is formed the gradient
composition layer in that the density of the aluminum oxide forming
the oxygen barrier layer 70 decreases continuously and the density
of the zirconium oxide forming the thermal stress relieving layer
22 increases continuously from the oxygen barrier layer 70 toward
the thermal stress relieving layer 22.
[0070] The interface between the zirconium oxide ingot 41 and the
hafnium oxide ingot 42 is configured to have the prescribed angle
.theta. with respect to the central axis of the columnar stacked
body, so that the vapor 67 having a composition containing both
components, the zirconium oxide and the hafnium oxide, can be
formed at the time when the interface becomes the vapor 67. The
component composition of the vapor 67 when the ingot 65 of the
portion having the prescribed angle .theta. has the density of the
zirconium oxide decreased continuously and the density of the
hafnium oxide increased continuously. Thus, the gradient
composition layer is formed between the thermal stress relieving
layer 22 and the thermal barrier layer 23, in which the density of
the zirconium oxide which forms the thermal stress relieving layer
22 decreases continuously and the density of the hafnium oxide
which forms the thermal barrier layer 23 increases continuously
from the thermal stress relieving layer 22 toward the thermal
barrier layer 23.
[0071] Adjustment of the above-described prescribed angles .theta.,
.gamma. allows adjustment of the thickness of the gradient
composition layer, the density gradient of the aluminum oxide and
the zirconium oxide in the gradient composition layer, and the
density gradient of the zirconium oxide and the hafnium oxide.
Besides, the stacked quantity of the individual ingots 41, 42, 66
other than the portions contacted at the prescribed angles .theta.,
.gamma. in the ingot 65 can be adjusted to adjust the thickness of
the oxygen barrier layer 70, the thermal stress relieving layer 22
and the thermal barrier layer 23. Depending on the characteristics,
for example, heat cycle life, thermal barrier characteristic,
thermal shock resistance and the like which are required for the
base material 20 to be coated, the coating can be applied by
appropriately adjusting the prescribed angles .theta., .gamma. in
the ingot 40 and the stacked quantity of the aluminum oxide ingot
66, the zirconium oxide ingot 41 or the hafnium oxide ingot 42 at
the portion other than the portions contacted at the prescribed
angles .theta., .gamma..
[0072] As described above, according to the ceramic-coated member
60 of the second embodiment, the boundary portion 71 and its
neighborhood between the oxygen barrier layer 70 and the thermal
stress relieving layer 22 can be formed as the gradient composition
layer where the density of the aluminum oxide which forms the
oxygen barrier layer 70 is decreased continuously and the density
of the zirconium oxide which forms the thermal stress relieving
layer 22 is increased continuously from the oxygen barrier layer 70
toward the thermal stress relieving layer 22. Thus, the
concentration of a thermal stress in the contacted part of the
coatings of the different materials is relieved, and the heat cycle
characteristic can be improved substantially.
[0073] And, the boundary portion 24 and its neighborhood between
the thermal stress relieving layer 22 and the thermal barrier layer
23 can be formed as the gradient composition layer where the
density of the zirconium oxide which forms the thermal stress
relieving layer 22 decreases continuously and the density of the
hafnium oxide which forms the thermal barrier layer 23 increases
continuously from the thermal stress relieving layer 22 toward the
thermal barrier layer 23. Thus, the concentration of a thermal
stress in the contacted part of the coatings of the different
materials is relieved, and the heat cycle characteristic can be
improved substantially.
[0074] A surface of the ceramic-coated member 10 is formed of the
thermal barrier layer 23 which is formed of hafnium oxide having
excellent heat resistance and low thermal conductivity, the thermal
stress relieving layer 22 which is formed of zirconium oxide having
low thermal conductivity and a thermal expansion coefficient larger
than that of the hafnium oxide is formed on the metal layer side of
the thermal barrier layer 23, and the oxygen barrier layer 70 which
is formed of the aluminum oxide having a thermal expansion
coefficient larger than that of the zirconium oxide is formed on
the metal layer side of the thermal stress relieving layer 22.
Accordingly, even if the ceramic-coated member 10 is used at a high
temperature for a long time, it maintains the excellent thermal
barrier characteristic and has the excellent heat cycle
characteristic.
[0075] The above-described ceramic-coated member 60 having the
gradient composition layer (the boundary portions 24, 71 and their
neighborhoods) can be produced by using the ingot 65 which has the
aluminum oxide ingot 66, the zirconium oxide ingot 41 and the
hafnium oxide ingot 42 stacked in this order in a columnar form
such that the aluminum oxide ingot 66 is evaporated first by the
electron-beam physical vapor deposition, and the interface between
the aluminum oxide ingot 66 and the zirconium oxide ingot 41 and
the interface between the zirconium oxide ingot 41 and the hafnium
oxide ingot 42 have the prescribed angles .theta., .gamma. with
respect to the central axis of the columnar laminated body.
[0076] It is described below that the ceramic-coated member
according to the invention, which is coated with ceramic using the
ingot which has the interface of the individual ingots of the
ceramic described above determined to have 45.degree. to 85.degree.
with respect to the central axis of the columnar stacked body, has
an excellent heat cycle characteristic.
EXAMPLE 1
[0077] A production method of test pieces 1 used in Example 1 is
described with reference to a sectional view showing an overview of
the electron-beam physical vapor deposition for the production of
the ceramic-coated member 10 shown in FIG. 2.
[0078] The oxidation resistant layer 21 which was a coating having
a thickness of about 100 .mu.m and formed of an Ni--Co-base alloy
having excellent corrosion resistance and oxidation resistance was
formed by plasma spraying on the surfaces of a disk-shaped base
material 20 having a diameter of 2.54 cm (1 inch) and a thickness
of 5 mm and made of a Ni-base superalloy.
[0079] The base material 20 on which the oxidation resistant layer
21 was formed was attached to be rotatable with the center of the
disk-shaped base material 20 determined as the rotation axis within
the coating chamber of an electron-beam physical vapor deposition
apparatus. The base material 20 was rotated at about 10 rpm. The
zirconium oxide ingot 41 and the hafnium oxide ingot 42 were
stacked in a columnar shape in the water-cooled crucible 50 within
the coating chamber such that the zirconium oxide ingot 41 was
evaporated first. It was determined that the interface between the
zirconium oxide ingot 41 and the hafnium oxide ingot 42 became
85.degree. with respect to the central axis of the columnar stacked
body.
[0080] After the coating chamber was evacuated, the electron beam
45 was irradiated to the surface of the zirconium oxide ingot 41
inserted into the water-cooled crucible 50 to melt the zirconium
oxide so as to generate the vapor 46 of ingot material, thereby
forming the thermal stress relieving layer 22 of the zirconium
oxide on the surface of the oxidation resistant layer 21.
Subsequently, the ingot 40 was melted gradually to evaporate, and
the area including the interface between the zirconium oxide ingot
41 and the hafnium oxide ingot 42 was exposed to the electron beam
45 to generate the vapor 46 containing both of the zirconium oxide
and the hafnium oxide, thereby forming a gradient composition layer
in the boundary portion 24 and its neighborhood between the thermal
stress relieving layer 22 and the thermal barrier layer 23. In the
process of forming the above-described thermal stress relieving
layer 22 and gradient composition layer, the base material 20 was
kept at a temperature of 850 to 900.degree. C.
[0081] Besides, the ingot 40 was melted to evaporate so as to reach
the area formed of only the hafnium oxide ingot 42, and the hafnium
oxide was melted to generate the vapor 46 so as to form the thermal
barrier layer 23 of the hafnium oxide. In the process of forming
the thermal barrier layer 23, the base material 20 was kept at a
temperature of 900 to 950.degree. C.
[0082] The electron beam 45 was stopped immediately before the
hafnium oxide ingot 42 was completely evaporated and consumed.
[0083] The thermal stress relieving layer 22 formed by the
above-described electron-beam physical vapor deposition had a
thickness of about 200 .mu.m, the gradient composition layer formed
in the boundary portion 24 and its neighborhood had a thickness of
about 24 .mu.m, and the thermal barrier layer 23 had a thickness of
about 100 .mu.m.
[0084] The test pieces 1 produced by the above-described method
were used to conduct a heat cycle test. In the heat cycle test, the
individual test pieces 1 were placed and heated in an electric
furnace kept at a temperature of 1100.degree. C. for 30 minutes and
left in the atmosphere to cool to a temperature of 100.degree. C.
Subsequently, the test piece 1 having the temperature of
100.degree. C. was left standing in the electric furnace for 30
minutes and heated, and then left standing in the atmosphere until
the temperature became 100.degree. C. Thus, heating and cooling
were repeated, and the number of repeated times until the ceramic
coating layer formed of the test piece 1 was delaminated was
measured.
[0085] Table 1 shows the results of the heat cycle test. In Table
1, the number of white and black circles indicates the number of
test pieces undergone the heat cycle test under the same
conditions. The white circle means that no damage was caused by the
corresponding number of repeated times, and the black circle means
that delamination or localized swelling was caused by the
corresponding number of repeated times.
TABLE-US-00001 TABLE 1 Number of repetitions 10 20 30 40 50 75 100
125 150 200 E Test piece 1 .largecircle..largecircle.
.largecircle..largecircle. .largecircle..largecircle.
.largecircle..largecircle. .largecircle..largecircle.
.largecircle..largecircle. .largecircle..cndot. .cndot. Test piece
2 .largecircle..largecircle. .largecircle..largecircle.
.largecircle..largecircle. .largecircle..largecircle.
.largecircle..largecircle. .largecircle..largecircle.
.largecircle..largecircle. .largecircle..cndot. .cndot. Test piece
3 .largecircle..largecircle. .largecircle..largecircle.
.largecircle..largecircle. .largecircle..largecircle.
.largecircle..largecircle. .largecircle..largecircle.
.largecircle..largecircle. .largecircle..largecircle.
.largecircle..largecircle. .largecircle..cndot. Test piece 4
.largecircle..largecircle. .largecircle..largecircle.
.largecircle..largecircle. .largecircle..largecircle.
.largecircle..largecircle. .largecircle..largecircle.
.largecircle..largecircle. .largecircle..largecircle.
.largecircle..largecircle. .largecircle..largecircle. CE Test piece
5 .largecircle..largecircle. .largecircle..largecircle.
.largecircle..cndot. .largecircle. .largecircle. .cndot. Test piece
6 .cndot..cndot. E = Example, CE = Comparative Example
[0086] Two test pieces 1 were tested under the same conditions, and
one of them had damage (delamination of coating) when the number of
repeated times was 100 as shown in Table 1. When the number of
repeated times was 125, the other test piece 1 had damage
(delamination of coating).
EXAMPLE 2
[0087] Test pieces 2 used in Example 2 were produced by the same
method as that used for the production of the test pieces 1 of
Example 1 except that the ingot 40 which was formed to have the
interface between the zirconium oxide ingot 41 and the hafnium
oxide ingot 42 with an angle of 80.degree. with respect to the
central axis of the columnar stacked body was used.
[0088] In the produced test pieces 2, the thermal stress relieving
layer 22 had a thickness of about 200 .mu.m, the gradient
composition layer formed in the boundary portion 24 and its
neighborhood had a thickness of about 36 .mu.m, and the thermal
barrier layer 23 had a thickness of about 100 .mu.m. The heat cycle
test method and the measuring conditions were same as those of
Example 1.
[0089] Two test pieces 2 were tested under the same conditions, and
one of them had damage (delamination of coating) when the number of
repeated times was 125 as shown in Table 1. When the number of
repeated times was 150, the other test piece 2 had damage
(delamination of coating).
EXAMPLE 3
[0090] Test pieces 3 used in Example 3 were produced by the same
method as that used for the production of the test pieces 1 of
Example 1 except that the ingot 40 which was formed to have the
interface between the zirconium oxide ingot 41 and the hafnium
oxide ingot 42 with an angle of 75.degree. with respect to the
central axis of the columnar stacked body was used.
[0091] In the produced test pieces 3, the thermal stress relieving
layer 22 had a thickness of about 200 .mu.m, the gradient
composition layer formed in the boundary portion 24 and its
neighborhood had a thickness of about 50 .mu.m, and the thermal
barrier layer 23 had a thickness of about 100 .mu.m. The heat cycle
test method and the measuring conditions were same as those of
Example 1.
[0092] Two test pieces 3 were tested under the same conditions, and
one of them had damage (delamination of coating) when the number of
repeated times was 200 as shown in Table 1.
[0093] A cross section of the test piece 3 was observed through a
scanning electron microscope (SEM). The boundary portion 24 and its
neighborhood of the test piece 3 were measured for element
distribution by an electron prove micro analyzer (EPMA). The
results of the observation and element distribution measurement are
described later.
EXAMPLE 4
[0094] A production method of test pieces 4 used in Example 4 is
described with reference to a sectional view showing an overview of
the electron-beam physical vapor deposition for the production of
the ceramic-coated member 60 shown in FIG. 3.
[0095] An oxidation resistant layer 21 which is a coating having a
thickness of about 100 .mu.m and formed of an Ni--Co-base alloy
having excellent corrosion resistance and oxidation resistance was
formed on the surfaces of a disk-shaped base material 20 having a
diameter of 2.54 cm (1 inch) and a thickness of 5 mm and formed of
an Ni-base superalloy by plasma spraying.
[0096] The base material 20 on which the oxidation resistant layer
21 was formed was attached to be rotatable with the center of the
disk-shaped base material 20 determined as the rotation axis within
the coating chamber of an electron-beam physical vapor deposition
apparatus. The base material 20 was rotated at about 10 rpm. An
aluminum oxide ingot 66, the zirconium oxide ingot 41 and the
hafnium oxide ingot 42 were stacked in this order in a columnar
shape in the water-cooled crucible 50 within the coating chamber
such that the aluminum oxide ingot 66 is evaporated first. It was
determined that the interface between the aluminum oxide ingot 66
and the zirconium oxide ingot 41 and the interface between the
zirconium oxide ingot 41 and the hafnium oxide ingot 42 became
85.degree. with respect to the central axis of the columnar stacked
body.
[0097] After the above-described coating chamber was evacuated, the
electron beam 45 was irradiated to the surface of the aluminum
oxide ingot 66 of the ingot 65 inserted into the water-cooled
crucible 50 to melt the aluminum oxide so as to generate the vapor
67, thereby forming the oxygen barrier layer 70 of the aluminum
oxide on the surface of the oxidation resistant layer 21.
Subsequently, the ingot 65 was melted gradually to evaporate, and
the area including the interface between the aluminum oxide ingot
66 and the zirconium oxide ingot 41 was exposed to the electron
beam 45 to generate the vapor 67 containing both of the aluminum
oxide and the zirconium oxide, thereby forming a gradient
composition layer in the boundary portion 71 and its neighborhood.
In the process of forming the above-described oxygen barrier layer
70 and gradient composition layer, the base material 20 was kept at
a temperature of 600 to 800.degree. C.
[0098] Besides, the ingot 65 was melted to evaporate so as to reach
the area formed of only the zirconium oxide ingot 41, and the
zirconium oxide was melted to generate the vapor 67 so as to form
the thermal barrier layer 22 of the zirconium oxide. Subsequently,
the ingot 40 was melted gradually to evaporate to reach the area
including the interface between the zirconium oxide ingot 41 and
the hafnium oxide ingot 42 and to generate the vapor 67 containing
both of the zirconium oxide and the hafnium oxide, thereby forming
a gradient composition layer in the boundary portion 24 and its
neighborhood. In the process of forming the above-described thermal
stress relieving layer 22 and gradient composition layer, the base
material 20 was kept at a temperature of 700 to 900.degree. C.
[0099] Besides, the ingot 65 was melted to evaporate so as to reach
the area formed of only the hafnium oxide ingot 42, and the hafnium
oxide was melted to generate the vapor 67 so as to form the thermal
barrier layer 23 of the hafnium oxide. In the process of forming
the thermal barrier layer 23, the base material 20 was kept at a
temperature of 750 to 950.degree. C.
[0100] And, the electron beam 45 was stopped immediately before the
hafnium oxide ingot 42 was completely evaporated and consumed.
[0101] The oxygen barrier layer 70 formed by the above-described
electron-beam physical vapor deposition had a thickness of about 20
.mu.m, the thermal stress relieving layer 22 had a thickness of
about 200 .mu.m, the gradient composition layer had a thickness of
about 24 .mu.m, and the thermal barrier layer 23 had a thickness of
about 100 .mu.m.
[0102] The test pieces 4 produced by the above-described method
were used to conduct a heat cycle test. The heat cycle test method
and the measuring conditions were same as those of Example 1.
[0103] When the test pieces 4 were tested for the number of
repeated times of 200, they had no damage as shown in Table 1.
COMPARATIVE EXAMPLE 1
[0104] Test pieces 5 used in Comparative Example 1 were produced by
the same method as that used for the production of the test pieces
1 of Example 1 except that the ingot 40 which was formed to have
the interface between the zirconium oxide ingot 41 and the hafnium
oxide ingot 42 with an angle of 90.degree. with respect to the
central axis of the columnar stacked body was used. Here, the fact
that the interface between the zirconium oxide ingot 41 and the
hafnium oxide ingot 42 becomes 90.degree. to the central axis of
the columnar stacked body means that the interface between the
zirconium oxide ingot 41 and the hafnium oxide ingot 42 is
horizontal.
[0105] In the produced test pieces 5, the thermal stress relieving
layer 22 had a thickness of about 100 .mu.m, and the thermal
barrier layer 23 had a thickness of about 100 .mu.m. The heat cycle
test method and the measuring conditions were same as those of
Example 1.
[0106] Two test pieces 5 were tested under the same conditions, and
one of them had damage (delamination of coating) when the number of
repeated times was 30 as shown in Table 1. When the number of
repeated times was 75, the other test piece 5 had damage
(delamination of coating).
COMPARATIVE EXAMPLE 2
[0107] Test pieces 6 used in Comparative Example 2 were produced
from an ingot which was prepared with the positions of the
zirconium oxide ingot 41 and the hafnium oxide ingot 42 of the
ingot 40 used in Example 1 reversed. In other words, the test
pieces 6 were produced from the ingot which had the hafnium oxide
ingot 42 and the zirconium oxide ingot 41 stacked in a columnar
shape in the water-cooled crucible 50 such that the hafnium oxide
ingot 42 was evaporated first. The ingot was formed such that the
interface between the hafnium oxide ingot 42 and the zirconium
oxide ingot 41 became 85.degree. with respect to the central axis
of the columnar stacked body.
[0108] After the above-described coating chamber was evacuated, the
electron beam 45 was irradiated to the surface of the hafnium oxide
ingot 42 of the ingot inserted into the water-cooled crucible 50 to
melt the hafnium oxide so as to generate the vapor 46, thereby
forming a coating layer of the hafnium oxide on the surface of the
oxidation resistant layer 21. Subsequently, the ingot was melted
gradually to evaporate so as to reach the area including the
interface between the hafnium oxide ingot 42 and the zirconium
oxide ingot 41 and to generate the vapor 46 containing both of the
hafnium oxide and the zirconium oxide, thereby forming a gradient
composition layer in the boundary portion 24 and its neighborhood.
In the process of forming the above-described coating layer and
gradient composition layer, the base material 20 was kept at a
temperature of 750 to 950.degree. C.
[0109] Besides, the ingot was melted to evaporate so as to reach
the area formed of only the zirconium oxide ingot 41, and the
zirconium oxide was melted to generate the vapor 46 so as to form
the coating layer of the zirconium oxide. In the process of forming
the coating layer, the base material 20 was kept at a temperature
of 700 to 900.degree. C.
[0110] And, the electron beam 45 was stopped immediately before the
zirconium oxide ingot 41 was completely evaporated and
consumed.
[0111] The coating layer of the hafnium oxide formed by the
above-described electron-beam physical vapor deposition had a
thickness of about 100 .mu.m, the gradient composition layer had a
thickness of about 24 .mu.m, and the coating layer of the zirconium
oxide had a thickness of about 200 .mu.m.
[0112] The test pieces 6 produced by the above-described method
were used to conduct a heat cycle test. The heat cycle test method
and the measuring conditions were same as those of Example 1.
[0113] Two test pieces 6 were tested under the same conditions, and
both of them had damage (delamination of coating) when the number
of repeated times was 10 as shown in Table 1.
SUMMARY OF EXAMPLE 1 TO EXAMPLE 4 AND COMPARATIVE EXAMPLE 1 TO
COMPARATIVE EXAMPLE 2
[0114] As shown in Table 1, it was found that the test pieces (test
pieces 1 to 4) used in Example 1 to Example 4 of the invention had
good heat cycle characteristic. It was also found from the results
of Example 4 that better heat cycle characteristic could be
obtained by disposing the oxygen barrier layer 70 formed of
aluminum oxide between the oxidation resistant layer 21 and the
thermal stress relieving layer 22.
[0115] It was found from the results of Example 1 to Example 3 of
the invention that the heat cycle characteristic became better as
the angle .theta. of the interface between the zirconium oxide
ingot 41 and the hafnium oxide ingot 42 became smaller with respect
to the central axis of the columnar stacked body. It is considered
that the tendencies of the compositions to change discontinuously
as shown in FIG. 11A and FIG. 11B were decreased to become
continuous as the angle .theta. became smaller, and the
concentration of the thermal stress in the interface between the
different materials was lowered.
[0116] FIG. 5 shows a reflected electron image which is a result of
observing a cross section of the test piece 3 of Example 3 by the
SEM. FIG. 6 shows the results obtained by measuring the element
distribution in the boundary portion 24 and its neighborhood of the
test piece 3 performed in Example 3.
[0117] As shown in FIG. 5, it was found that the thermal barrier
layer 23 and the thermal stress relieving layer 22 have
therebetween the area having a structure different from the
individual layers in the boundary portion 24 and its neighborhood.
It was also found from the results of measuring the element
distribution shown in FIG. 6 that in the boundary portion 24 and
its neighborhood, the intensity of zirconium corresponding to the
density of the zirconium oxide which formed the thermal stress
relieving layer 22 decreased continuously from the thermal stress
relieving layer 22 toward the thermal barrier layer 23, and the
intensity of hafnium corresponding to the density of the hafnium
oxide which formed the thermal barrier layer 23 increased
continuously. In other words, it was found that the boundary
portion 24 and its neighborhood formed the gradient composition
layer where the densities of the zirconium oxide and the hafnium
oxide changed continuously.
[0118] FIG. 7 shows a relationship between the angle .theta. formed
by the interface between the zirconium oxide ingot 41 and the
hafnium oxide ingot 42 with respect to the central axis of the
columnar stacked body and the thickness of the gradient composition
layer formed when the ingot 40 having that angle was used. The
angle of 85.degree. corresponds to the thickness of the gradient
composition layer of the test piece 1, the angle of 80.degree.
corresponds to the thickness of the gradient composition layer of
the test piece 2, and the angle of 75.degree. corresponds to the
thickness of the gradient composition layer of the test piece
3.
[0119] It is apparent from FIG. 7 that the boundary portion 24 and
its neighborhood, namely the thickness of the gradient composition
layer, can be controlled by varying the angle .theta.. It was also
found that when the angle .theta. was increased, the gradient
composition layer could be made thin, and when the angle .theta.
was decreased, the gradient composition layer could be made thick.
Thus, the gradient composition layer can be determined to have an
appropriate thickness in compliance with, for example, the
characteristics such as heat cycle life, thermal barrier
characteristic and thermal shock resistance required by the
ceramic-coated member.
[0120] The test piece 6 of Comparative Example 2 having the coating
layer of zirconium oxide on the coating layer of hafnium oxide had
a good gradient composition layer formed on both of the boundary
portion and its neighborhood (not shown), but the heat cycle life
was considerably inferior in comparison with the test pieces (test
pieces 1 through 3) of Examples 1 through 3. It seems from the
results that a thermal expansion coefficient (about
6.times.10.sup.-6/.degree. C.) of the hafnium oxide is small in
comparison with a thermal expansion coefficient (about
10.times.10.sup.-6/.degree. C.) of the zirconium oxide or a thermal
expansion coefficient (about 15.times.10.sup.-6/.degree. C.) of the
metal base material, and a large thermal stress is generated in the
coating layer of the hafnium oxide which is sandwiched between the
coating layer of the zirconium oxide having a large thermal
expansion coefficient and the metal base material. Therefore, it
was found effective to select a material such that the thermal
expansion coefficients of the individual layers decrease gradually
from the side of the metal base material toward the surface in
order to suppress the thermal stress generated in the individual
layers similar to the test pieces (test pieces 1 through 3) of
Example 1 through Example 3.
[0121] Although the invention has been described above by reference
to the embodiments of the invention, the invention is not limited
to the embodiments described above. It is to be understood that
modifications and variations of the embodiments can be made without
departing from the spirit and scope of the invention.
* * * * *